The Sayano-Shushenskaya dam hydro-electric power station accident

The construction of the power plant includes an arch gravity dam and a spillway (under construction). The arch gravity dam is 245.5 metres high with a solid left bank dam 246.1 metres long, a power dam of 331.8 metres long a spillway dam of 189.6 metres long and a solid right bank dam of 298.5 metres long. The dam is built so strong enough to withstand earthquakes of up to 8 on the Richter scale.

The hydro power plant was built with ten turbines. The turbine No 2 started having problems shortly after its installation due to defects in its seals and shaft vibrations. The cavities and crack on the turbine wheel were completely reconditioned in 2000. Despite these efforts, turbine No 2 continued to have problems, leading to further repairs in 2005 and 2009, during which again turbine blades were repaired. But still the turbine experienced vibrations due to new cracks and cavities, which did not exceed the threshold limit. But in July 2009 the vibrations exceeded the threshold value and continued to increase. It is believed that there were several attempts to shut down the turbine.

But on the 17^th of august 2009, despite all these attempts, the vibration increased a lot (four times more than the other turbines) pushing the rotor inside the turbine up, thereby pushing the turbine cover which was kept in place by 80 bolts of 8 centimetres diameter. There was a loud bang of sound when the turbine cover was pushed up, after which the 900 ton rotor was shot out of its location due to the force of the flood, bouncing it off the ceiling of the machine room destroying the entire concrete and steel turbine room structure flooding the machinery hall and the rooms below its level. There was a complete blackout because the power output fell to zero. So the emergency generators were started to open the spillway gates of the dam. The accident also created a transformer explosion which in turn created a large oil slick (transformer fluid that leaked from one of the hydroelectric station's damaged units) that floated down the YeniseiRiver, which flows north through Siberia to the Arctic. It is estimated that 40 tons of transformer oil were spilled into the river, killing an estimated 400 tons of trout in two fisheries.This disaster has lead to the death of 74 people and one still missing.

Flood water was pumped out of the engine room by the 24^th of August 2009, while the search and rescue operation was complete by the 28^th of august 2009.

1. Former general director of the plant claims that the manufacturing defects in the turbines were the cause, and also said that these turbine blades were not reliable.
2. Another former director claims the incorrect starting process of the turbine to be the reason for this disaster.
3. A website supporting the rebel groups in Chechnya claimed on 21^st of August 2009 that they were the reason for the blast, which was dismissed as senseless by the authorities.
4. On the 11 September 2009, RusHydro failed to accept dam displacement as the reason for this disaster.

But the cause of the disaster according to RusHydro is, spouting of water from the socket of turbine No 2. A Russian newspaper has written as the cause to be turbine vibration, as a result of which cracks appeared in the bolts that were used to keep the turbine in place. It is also believed that the ongoing problems with turbine no 2 was very well known to the plant personnel for almost 10 years.

This turbine failure in the hydro power plant led to serious destructions which include fatalities, power shutdown, damages, Impact on environment and finance.

1. 74 people are reported dead including one missing bur assumed to be dead.
2. severe damage was posed to many of the 10 turbines and a few transformers.
3. Companies that depended on this plant for cheaper power supplies face serious production issues, and also situations where they have to pay higher electricity charges.
4. Tonnes of oil spill from the transformer led to killing tons of trout fish in two fisheries, and also other serious impacts on wildlife.
5. RusHydro experience serious drop in its share prices and lost millions, which it will be continuing to lose for the years to come.
6. Russian government along with RusHydro is believed to pay compensation to victim’s families and also to survivors.
7. The director of the plant was replaced.

All these serious destructions to the power plant have brought the operation of the plant to a halt, and the complete recovery is expected to take decades. There are steps being taken to operate a few turbines which can be operated without replacements, while replacements of other damaged ones are expected to take a few years.